1. Field of the Invention
The present invention relates to an optical module for use in optical communications. More particularly, the present invention relates to an optical module which can be locked in a cage for accommodating the case of the optical module.
2. Description of the Related Art
One of conventionally known optical modules for use in optical communications is an optical transceiver which comprises a light emitting element and a light receiving element for performing opto-electric conversion to make communications through optical fibers.
One type of such optical transceivers comprises an optical unit, including a light emitting element and a light receiving element, contained in a case, and is structured for removable accommodation in a cage mounted on a substrate. The cage has a socket mounted on the substrate, such that the optical transceiver plugged into the cage causes its connection terminals to come into connection with the socket. The optical transceiver thus constructed converts an optical signal communicated to/from an optical fiber to an electric signal communicated to/from the substrate, and vice versa to enable optical communications.
However, if an optical transceiver is withdrawn from the cage during the operation of the optical transceiver, a communication device including the optical transceiver can fail, needless to say that a communication is interrupted in the middle. To prevent such a trouble, the optical transceiver must be securely fixed within the cage at least during its operation.
In recent years, an industrial standardization organization has developed a standard called MSA (MultiSource Agreement) for SFP (Small Form-factor Pluggable) transceiver, by way of example, for making optical transceivers provided from respective companies compatible with one another. MSA defines the shape and dimensions of SFP transceivers and cages for accommodating the SFP transceivers. According to the SFP MSA standard, an optical transceiver is provided with a protrusive latch formed on a bottom surface thereof, while a cage is provided with a spring plate formed with a retaining hole therethrough for retaining the latch therein, so that when the optical transceiver is inserted into the cage, the latch of the optical transceiver can fit into the retaining hole of the cage to lock the optical transceiver in the cage. On the other hand, for removing the optical transceiver from the cage, any member must be used to release the latch from the retaining hole of the spring plate to unlock the optical transceiver from the cage.
FIG. 1 is a perspective view illustrating a conventional optical transceiver disclosed in U.S. Pat. No. 6,434,015 with its bottom surface oriented upward.
The conventional optical transceiver illustrated in FIG. 1 comprises housing 101 provided for accommodating a light emitting element and a light receiving element and formed with latch 114; and ejector 170 for removing latch 114 from a retaining hole (not shown) of a cage. Ejector 170 is arranged in an ejector sheet formed in lower portion 111 of housing 101, such that depression onto push plate 179 arranged at the rear end of ejector 170 enables the leading end of ejector 170 to extend to the vicinity of latch 114 from the interior of the ejector sheet. When the leading end of ejector 170 is protruded while latch 114 of the optical transceiver is retained in the retaining hole formed through the spring plate of the cage, the spring plate is bent to release latch 114 from the retention by the retaining hole.
Thus, this optical transceiver can be withdrawn from the cage by pushing push plate 179 of ejector 170 in a direction indicated by an arrow A in FIG. 1 to protrude the leading end thereof to the vicinity of latch 114, and releasing latch 114 from the retention by the retaining hole formed through the spring plate of the cage.
Another optical module has been also proposed by the present applicant for permitting the user to remove the optical module from a cage through simple operations and for installing a plurality of the optical modules in a single communication device at a higher density (refer to the Japanese patent application No. JP-2002-334967-A filed by the present applicant).
FIG. 2 is a diagram illustrating an optical module described in the patent application JP-2002-334967-A. The optical module described in the prior application has a locking mechanism which comprises locking member 204 swingably attached to case 201 and having latch 204d for retention in retaining hole 210a formed in cage 210; and lever 203 for moving locking member 204 to release latch 204d from retaining hole 210a in which latch 204d is retained. This locking mechanism is designed such that as the user pulls lever 203 forward of case 201, i.e., in a direction in which the optical module accommodated in cage 210 is withdrawn from cage 210, latch 204d retained in retaining hole 210a comes off retaining hole 210a. A movable range of lever 203 is limited within a region forward of a front end surface of case 201.
According to the optical module designed as described above, as lever 203 is pulled forward of case 201 to move pivotal shaft 203a of lever 203 to a position at which pivotal shaft 203a comes into abutment to a front end within cutout groove 202, pivotal shaft 203a pushes down cam face 204f formed in front section 204a of locking member 204. This causes locking member 204 to swing about shaft 205 within groove 206 to lift up spring portion 204e and rear section 204c. Then, spring portion 204e comes into abutment to groove 201c formed in a bottom surface of case 201 to bend, causing latch 204d on the bottom surface of rear section 204c to come off retaining hole 210a of cage 210. Consequently, the optical module is released from the locking by the locking mechanism.
While lever 203 is kept pulled forward of case 201, the optical module remains released from the locking by the locking mechanism, so that the optical module can be withdrawn from cage 210 by pulling lever 203 forward of case 201 in this released state maintained.
However, An SFP optical transceiver conforming to the MSA standard, as disclosed in FIG. 1, should have a height of about 10 mm and a width of about 14 mm, i.e., the SFP optical transceiver itself is small in size, so that ejector 170 (see FIG. 1) disposed in such a small optical transceiver must be a miniature component. For this reason, it must be a finger tip (or even a nail tip in some cases) that should depress push plate 179 of ejector 170 illustrated in FIG. 1. However, there is few clearance between the substrate on which the cage is mounted and the bottom surface of the optical transceiver, when the optical transceiver is mounted in the cage, so that the finger tip may not successfully reach the push plate 179 of ejector 170, thus experiencing difficulties in performing operations for unlocking the optical transceiver from the cage.
The locking mechanism for an optical module described in FIG. 2, on the other hand, is made up of two components which are the aforementioned locking member 204 and lever 203, however, such a locking mechanism is preferably made up of the least possible number of components from a view point of the tendency of reducing a material cost and the number of manufacturing steps of the optical module.
In addition, the optical transceiver is typically small in size as mentioned above, and lever 203 is a miniature component. Such a miniature structure forces the user to hold lever 203 with tips of fingers for manipulations. Thus, the user could more readily remove the optical transceiver if the optical transceiver could be unlocked from the cage without the need for manipulating such lever 203.
The optical module illustrated in FIG. 2 limits the movable range of lever 203 within a region forward of the front end surface of case 201 to save the space required to install the optical module in a communication device, thereby making it possible to install a plurality of the optical modules in a communication device at a high density. However, if lever 203 itself can be omitted from the optical module, a larger number of the optical modules can be installed in a communication device at a higher density.